Apparatus, such as a ladder, comprising extendable legs

ABSTRACT

A supporting element for an object includes a first leg member and a second leg member. The first leg member is axially movable relative to the second leg member for axially extending the support member. The first leg member includes a house slidably arranged for receiving the second leg member. The house includes a locking element having a locking position for locking the relative axial movement of the first leg member with respect to the second leg member, and an open position for enabling relative axial movement of the two members. A catch may be provided in the locking element. The catch may be tiltably movable within the house for alternately acquiring the locking position and the open position of the locking element. The catch may include a cavity receiving the second leg, wherein the cavity has a stopping surface engaging at least opposed perimeter parts of the second leg member in a locking position of the locking element.

The invention relates to an apparatus comprising a frame having at leastthree legs, each of the three legs being individually and selectivelyaxially extendible for adjusting the length of each of the at leastthree legs.

A supporting element, an apparatus and a locking element of theaforementioned kind are well known from the prior art. The supportingelement may for instance be an extendable leg member for a table or aladder. The extendable leg member may be used for stabilizing the ladderor table when positioned on an uneven surface. By extending one or morelegs of the object, it will be possible to carefully position the objectin a desired manner. Furthermore, the extendable leg member may be usedfor positioning a surface of the object (such as a table top, or abucket tray) in a level position.

In one embodiment, the leg from the prior art comprises two leg members,that may be slidably connected to each other. A fixation or lockingmechanism may be provided for securing the two leg parts to each other,such that the extendable leg member may be fixed at a desired length.The fixation may consist of a pin or screw that is entered into holesprovided on one or both leg parts.

Furthermore, a table or a ladder having one or more extendible legs isalso known from prior art. By adjusting the length of one or more legs,the ladder may be positioned in a desired fashion.

It is a drawback of the prior art legs that adjusting the length thereofmay be laborious and time consuming.

It is a drawback of the known apparatuses with a plurality of extendiblelegs, that the positioning of the object may be laborious. For instance,when positioning a table or a ladder on an uneven ground, it may berequired that a plurality of legs are adjusted.

This may prove to be difficult, since the user must decide the order oflegs to be adjusted, and to what extend each leg needs to be adjusted,before the object is in the desired position.

It is an object of the invention to provide an apparatus comprising a anadjustable leg, in which at least one of the known drawbacks isresolved.

In an embodiment, the apparatus comprises a frame having at least threelegs for positioning the apparatus on a surface. Each of the at leastthree legs can be individually and selectively axially extendible foradjusting the length of each of the legs. Each leg may comprise atransmission element and a the locking element. The locking element hasa locking position for locking the axial extension of the leg and has anopen position for enabling axial extension of the leg.

In an embodiment a transmission element connects the locking mechanismsin the at least three legs to a central operating mechanism foractivating and deactivating each locking element. The central operatingmechanism is arranged for activating or deactivating each lockingelement simultaneously. In this fashion, an apparatus, such as a ladder,a table or a tripod, is obtained, wherein each locking element of eachextendible leg may be unlocked at once, using only a central operatingelement.

The central operation element allows a one operation locking of severallegs with a desired length.

Additionally, each leg may be extended individually, meaning that thelength of each of the supporting elements may be arbitrarily chosen bythe user. The length of one supporting element is not dependent on thelength of another supporting element. This, in combination with thecentral operating element, enables the user to relatively easily andquickly position the apparatus in a desired position. For instance, itmay be used for positioning a table or a tripod in a level position, orfor positioning a ladder in a stable position on an uneven ground.

According to an embodiment the apparatus comprises at least two legsthat are hingebly connected with respect to each other. Further the atleast two legs each comprise at least one supporting element comprisingthe locking system according to the invention. The supporting elementsof the individual hingeable legs are connected to the central operationmechanism, allowing simultaneous operation of the locking element ineach of the hingeable legs.

It is possible that the operating mechanism comprises an operatinghandle that is connected to a rod. The rod may be rotatably attached tothe frame. The rod may be attached to the frame by means of bearings.The rod may comprise at least two pushing blocks that are positioned ata distance from each other. Each pushing block is arranged for engagingone of the transmission elements. The operating mechanism is arrangedsuch that rotation of the rod by rotating the operating handle resultsin a translational movement of the transmission element by pushing ofthe pushing blocks. The transmission element is arranged such that atranslational movement of the transmission element results in tiltingmovement of the catch of the locking element. This way a rigid operatingand locking element is obtained, that is reliable and safe.

It is possible that the apparatus comprises a supporting platform, fromwhich the at least three legs extend downwardly. The supporting platformmay be used for positioning an object onto it. With the adjustablesupporting elements, it is relatively easy to position the supportingplatform level.

In one embodiment, the apparatus is a ladder. The ladder may comprisetwo, three or four supporting elements according to the invention. Theladder may be easily positioned on an uneven ground. When a centraloperating element is used, the ladder may be positioned relativelyquickly and easily.

In an embodiment the leg comprises a supporting element, comprising afirst leg member and a second leg member. The first leg member isaxially movable relative to the second leg member for axially extendingthe support member. The first leg member comprises a house that isarranged for slidably receiving the second leg member. The housecomprises a locking element having a locking position for locking therelative axial movement of the first leg member with respect to thesecond leg member, and having an open position for enabling relativeaxial movement of the two members. By positioning the locking element ina house, the locking element is less vulnerable to dirt and will stayrelatively clean. Hence, the locking element will wear out less,ensuring a secure functioning of the locking element.

In an embodiment the locking element may comprise a catch that istiltably movable within the house for alternately acquiring the lockingposition and the open position of the locking element. The catch may bea relatively flat plate. The catch may comprise a cavity receiving thesecond leg. The catch comprises a stopping surface surrounding at leasta part of the perimeter of the cavity. The cavity may be a hole in thecatch, or an open cavity in the catch. A part of the surface of thecatch surrounding the cavity may be the stopping surface. The stoppingsurface may be relatively small, and may comprise a relatively smallpart of the cavity surface, such as the edge of the cavity. The opencavity may be U-shaped. In the open position of the locking element, thestopping surface is not in contact with the second leg member, such thatthe second leg member may freely slide in the house. The catch may bearranged such that in a locking position of the locking element thestopping surface engages at least opposed perimeter parts of the secondleg member. Due to engaging opposed perimeter parts, the second legmember is fixed in the cavity. By tilting the cavity such that in alocking position the stopping surface engages opposed parts of thesecond leg member, a moment is exerted on the second leg member. Thismoment pushes the second leg member tightly to the house and thestopping surface (such as the edge) of the catch. The resulting staticfriction between the second leg member, and both the house and thestopping surface of the catch, ensures that a tight and safe fixation ofthe second leg member is possible. It is an additional advantage of theinvention that the supporting element may be infinitely adjustable, i.e.that the supporting element may be fixed in any desired position,without having to settle for discrete positioning of the supportingelement.

In an embodiment the stopping surface is relatively small, and comprisesthe edge of the cavity. The edge may be relatively sharp, such that in alocking position the edge is pressed into the second leg member. Theedge may cut into the second leg member. This ensures that a highlocking pressure is obtained, resulting in a good resistance againstrelative movement of the two leg members.

In an embodiment, the longitudinal axis of the cavity extends parallelto the second leg member in an open position. The catch may bepositioned perpendicular to the second leg in an open position, suchthat the cavity in the catch is parallel to the second leg. This way,the necessary space is provided for the second leg to move freely. Also,this way, only a small amount of tilting is needed for the catch betweena locking position and an open position. This way, the supportingelement may be designed in a relatively compact way.

In an embodiment, the locking element, and in particular the catch, isbiased towards a locking position. By biasing the locking elementtowards a locking position, a larger force is exerted on the second legmember in a locking position. The resulting static friction willtherefore also be increased, leading to a tighter fix of the second legmember. It may be possible that a spring or any other biasing element isprovided in the house. Multiple springs or biasing elements are ofcourse possible. The spring is arranged for pushing the catch towards alocking position, and for pushing the stopping surface of the catchfirmly on the outer surface of the second leg member, increasing thestatic friction. With this, a supporting element with a rigid lockingelement providing a secure fit is obtained.

It is possible that at least a part of the catch and/or at least a partof the second leg member is made out of hardened steel. Preferably, atleast the part of the catch engaging the second leg member, and the partof the second leg member engaged by the catch, are made out of hardenedsteel. The coefficient of friction between two surfaces that are bothmade out of hardened steel is relatively high. More specifically, thecoefficient of friction for dry static friction is relatively high inthis case, yielding a tight and secure fit.

In an embodiment, the leg member comprises a biasing element that biasesthe supporting element towards an axially extended position. The biasingelement may push the legs of the supporting element towards an axiallyextended position. When the locking element is idle (i.e. in an openposition) this may lead the second leg element to move outwards. It maybe possible that the supporting element moves towards a maximal extendedposition as a result of the force exerted by the biasing element.

Alternatively, it may be possible that the biasing element is arrangedfor balancing a certain weight that the supporting element is designedto support. This way, when the locking element is in an open position,the supporting element will neither extend nor shorten. This enables theuser to relatively easily position the supporting leg in a desiredposition. The user may unlock the locking element, and then only a smallamount of force is needed for adjusting the length of the supportingelement.

In an embodiment the biasing force is of similar strength as the masssupported with the supporting element. If an apparatus comprisesmultiple supporting elements or legs, the biasing force of the multiplesupporting elements combined corresponds with the supported mass. Thiswill allow a ‘floating sensation’ to the supporting element/apparatus,when the supporting element/apparatus is positioned on a surface and thelocking element is in the open position allowing the leg to be extendedor shortened, while the mass is supported by the biasing force. Anoperator can lift the apparatus upwardly or downwardly feeling little orno resistance.

In an embodiment, the locking element comprises an additional catch thatis tiltably movable within the house for alternately acquiring thelocking position and the open position of the locking element. Theadditional catch comprises a cavity receiving the second leg. Theadditional catch has a stopping surface surrounding a part of theperimeter of the cavity. The stopping surface may surround an additionalpart of the second leg member, compared to the first catch. The stoppingsurface may be arranged for engaging at least opposed perimeter parts ofthe second leg member in a locking position of the locking element. Anadditional catch will result in an even tighter fixation of the two legmembers. It is possible that the catches surround different longitudinalparts of the second leg member. For instance, the second leg member maybe fixed at two different axial locations, enabling a rigid and securefit of the leg member.

In an embodiment, the catch and the additional catch are arranged fortilting in opposite directions towards a locking position. This way, arelatively compact design may be possible. Additionally, it may bepossible that the catches engage the second leg member at differentangles. This way, the second leg member is fixed even more tightly, andaxial movement of the second leg member is prevented.

In an embodiment a biasing element, such as a spring, is positionedbetween the catch and the additional catch. As the biasing elementengages both catches, a biasing force biasing the catches away from eachother is obtained. Preferably the tilting the catches away from eachother corresponds to tilting the catches to the locking position. Insuch an arrangement therefore the biasing element biases the lockingelement to the locked position.

Further the biasing element is preferably a spring coil. The biasingelement biasing the locking element to the locked position can be springcoil positioned around a leg member. This results in a constructionalsimplification, easing assembly of the supporting element, in particularif a spring coil is used.

It is possible that the locking element comprises a cam that is providedin the house. In an embodiment the house comprises a cam engaging thecatch for operating the catch from a locking position to an openposition.

In an embodiment opposite sides of the cam may engage the two catches.The cam may be arranged for simultaneously tilting the two catches froma locking position to an open position. The cam enables that the twocatches are operated simultaneously. With this, a tight fixation of theleg members is relatively easily obtainable.

In an embodiment, the supporting element comprises a transmissionelement connected to the locking element and extending towards an outeredge of the leg member. The transmission element may be connected to anoperating element provided on the leg member for operating the lockingelement. This way, the operation of the locking element may be performedat a distance from the actual position of the locking element. Theoperating element may be provided in a position that is ergonomicallyreachable by the user, without compromising the compactness of thesupporting element. The ergonomical position of the operating elementensures that the supporting elements may be adjusted easily and safely.

In a preferred embodiment, the transmission element is connected to thecam. The transmission element may be connected to the cam by means of ahinge. The transmission element, such as a bar, a rod, a cable or thelike, may be arranged such that operating the operating element resultsin a desired movement of the cam, and furthermore in a tilting movementof one or more catches. The transmission element may be slidablyconnected to the house. The transmission element may be arranged suchthat it moves parallel to the first leg member for operating the lockingelement. The axial movement of the transmission element may betranslated via the cam in a tilting movement of one or more catches.This way, a relatively compact supporting element may be obtained.

Preferably, the transmission element is a rigid element, such as a baror a rod. A rigid element will transfer movements from the operatingmechanism to the locking element very accurately. The forces acting on arigid element will not deform the rigid member, as will be the case whenfor instance a cable is used. Repetitive strain and deformation of acable may ultimately lead to failure thereof. This limits the safety ofthe supporting element, which is undesired. A rigid transmission elementmay lead to a safer and more accurate supporting element.

According to an aspect of the invention, an apparatus is providedcomprising a frame having at least two legs. It is possible that atleast one leg comprises a supporting element according to the invention.The apparatus may be a ladder or a table. The supporting element may beeasily and safely adjusted, as has become apparent from the previousdescription. This way, it is relatively easy to position the apparatusin a desired position. Also, a substantial amount of weight may besupported by such a ladder. A weight of over 150 kg may easily besupported by such an apparatus, having a supporting element according tothe invention.

According to a further aspect an apparatus according to claim 20 isprovided. The apparatus according to claim 20 can have any of thefurther features of claims 1-19. This apparatus is advantageous as alocking element in a hingeable leg is operated from a distance.

Although the invention is described and will be described with respectto preferred embodiments, it will be clear that within the scope of theinvention, multiple and different embodiments are possible. It is a goalof this application to protect the embodiments described, theembodiments indicated by the claims, as well as equivalents thereof. Theperson skilled in the art will (now that the advantages of the inventionare known) be able to construct different embodiments. It is anintention of the inventor to also protect these embodiments with thisapplication.

In the above, as well as in the following description, aspects of theinvention are described and advantages of the measures are described.The inventor intends to protect all the mentioned and unmentionedadvantages that the invention has with respect to the state of the art,using this application and/or divisional applications.

The invention will be described by reference to the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of a ladder;

FIG. 2 is an exploded view in perspective of a ladder, showing in moredetail an embodiment of the supporting element with a locking elementand a operating mechanism;

FIG. 3 is a side elevation of a locking element according to anembodiment of the invention;

FIG. 4 a is a side elevation of the supporting element of FIG. 3 in alocked position;

FIG. 4 b shows a detail of the locking mechanism of FIG. 4 a;

FIG. 5 a is a side elevation of the supporting element of FIG. 3 in alocked position;

FIG. 5 b shows a detail of the locking mechanism of FIG. 5 a;

FIG. 6 shows a perspective view of an operating mechanism for operatinga locking element;

FIG. 7 is a side elevation of the operating mechanism of FIG. 6;

FIG. 8 a is a side view of another embodiment of a locking mechanism ina locked position; and

FIG. 8 b is a side view of the embodiment according to FIG. 8 a in anunlocked position.

FIG. 1 shows a ladder 1 in a perspective view. The ladder has a frame.The ladder 1 comprises two front legs 5 a,5 b and two rear legs 5 c,5 d.The front legs 5 a,5 b are horizontally spaced from each other byseveral steps 6 that may be positioned at regular longitudinal intervalsfrom each other. At the upper end of the two front legs, a bucket tray 9is provided. The front legs 5 a,5 b, the steps 6 and the bucket tray 9are part of a front frame. The rear legs 5 c,5 d are horizontally spacedfrom each other by two connecting bars 13. The rear legs 5 c,5 d andconnecting bars 13 are part of a rear frame. The front frame and rearframe are hingeably connected to each other by means of hinging points8. A top step 7 connects the front frame to the rear frame, and assuresa stable and fixed angular position between the front frame and the rearframe. To this end, two spacing members 14 are also provided between thefront frame and the rear frame. The top step 7 may be rotatablyconnected to the rear frame, in a manner that is well known to thoseskilled in the art. The top step may be detached from the front frame,enabling the rear frame to hinge over hinging points 8 towards the frontframe. This way, the ladder may be positioned in a folded position,wherein the rear legs are relatively closely spaced and parallel to thefront legs.

As is shown in FIG. 1, each leg 5 a-d comprises an extendable legportion 10 a-d. Each system of a leg 5 and an extendable leg portion 10forms a supporting element 2. The leg may be viewed as a first legmember, and the extendable leg portion may be viewed as a second legmember. The two leg members are a part of the supporting element 2. Eachleg portion 10 a-d has a foot portion 11 a-d. The extendable legportions 10 a-d may move axially relative to the legs 5 a-d. At one sideof front leg 5 b, an operating handle 3 is provided. As will bediscussed later, a locking mechanism 200 is provided for locking therelative axial movement of the extendable leg portion and the leg. Thelocking mechanism comprises a locking element. The operating handle 3 isused to lock and unlock the locking mechanism 200. In a locked position,the extendible leg parts are unable to move relative to the legs. In anunlocked position or open position, relative movement between the legsand the extendible leg parts is possible. The extendible part may beable to move a certain length with respect to the leg. The length overwhich movement is possible, may for instance be 20 cm. Other lengths arepossible.

In another embodiment a table having one or more legs, in particular oneor more hingeable legs connected thereto is provided. An centraloperating mechanism can be connected to the frame or tabletop.

FIG. 2 shows an exploded view of the ladder 1 from FIG. 1. Likewiseelements are referred to with similar numerals. In this figure, the topstep 7 and the front leg 5 b are removed, thereby showing in more detailthe operating mechanism 21 and locking mechanism 200 of the ladder 1.Each extendable leg portion 10 a-d comprises a sliding bar 16 that isslidably received in the locking element or locking mechanism 200. Aspring 17 is connected between a house of the locking mechanism 200 andthe lower part of the extendable leg portion 10 a-d. Another bar 15 isslidably received in the locking mechanism 200, and extends towards theupper part of the ladder 1. There, the bar 15 engages the operatingmechanism 21. The operating mechanism 21 comprises two rods 18. Each rod18 is rotatably connected between either the front or the rear legs. Asan example, the rod may be attached to the frame by means of bearings.The two rods are positioned parallel to each other, and are connected bymeans of a connecting rod 19. The rod 18 has at one end a handle 3. Thehandle 3 may be used to lock and open the operating mechanism 200, aswill be described later.

FIG. 3 shows a side elevation of an embodiment of a part of a supportingelement, comprising a locking mechanism 30 having a locking element 34,35. FIG. 4 a-b and FIG. 5 a-b show further details of the supportingelement 2 of FIG. 3. FIG. 4 shows the locking mechanism 30 in a lockedposition. FIG. 5 shows the locking mechanism 30 in an open position.Likewise elements are referred to with similar numerals. The lockingmechanism 30 comprises a house 32. It is noted that the figuresschematically show the locking mechanism and other parts. These figuresare not to scale. In the embodiment shown, the house 32 is attached tothe first leg member 22, as can be seen from FIG. 4 and FIG. 5. Thefirst leg member 22 and the second leg member 20 are part of thesupporting element 2. At one end of the house 32, a sliding bar 33 isslidably received. The sliding bar may slide in an axial direction. Atan upper end of the sliding bar, a stop is provided, to limit theextension (i.e. downward movement) of the sliding bar. The sliding bar33 is connected to a lower leg part 41. The sliding bar 33 and the lowerleg part 41 are part of a second leg member 20. The lower leg part 41has a foot part 42 for stable placement of the ladder, or another objectprovided with a supporting element 2, in a used position. Around thesliding bar 33 a spring 44 is positioned. The spring extends between theouter side of the house 32 and the upper part of the lower leg part 41.At the other end of the house 32, a transmission element 31, such as atransmission rod 31, is slidably received. In the house a spring 43 isprovided, thereby contacting one end of the transmission rod 31. Moreupwards, the transmission rod is also slidably received in a guidingblock 46. An upper end of the transmission rod 31 engages a pushingblock 50, that is connected to a turning bar 48. The pushing block 50and turning bar 48 may rotate around the centre line of the turning bar.It is possible that a corner of the pushing block rests on a surface ina locked position of the locking mechanism 30. For instance, it may bepossible that the lower right corner of the pushing block 50 may rest onthe guiding block 46, and/or that the upper right corner rests on theinner part of the first leg member 22, in a locked position of thelocking mechanism 30. This way, rotation of the pushing block in onedirection is prevented. This ensures that only a small rotationalmovement of the pushing block, and thus a small rotational movement ofthe operating handle 3, is sufficient for disengaging the lockingmechanism.

In the house, a cam 36 is connected to the transmission rod 31 at ahinge point 51. The cam 36 may engage two catches 34,35. One catch 34 isprovided at an upper end of the cam, and one catch 35 is provided at alower end of the cam 36. An upper side 141 of the cam engages catch 34,and a lower side 142 of the cam 36 engages catch 35. The cam may be madein the shape of a butterfly, i.e. having two legs that extend round thesliding bar 33. Each catch 34,35 has one side thereof positioned in agroove 52, 53 of the house. The catch 34,35 may tilt, or rotate, in thehouse around a rotation axis formed by the lengthwise direction of thegroove 52, 53. It is noted that in the embodiment shown, the catch 34,35has no fixed axis of rotation within the housing. The catch is notconnected to the house, but may freely move in the house 34 and in thecavity 52. The outer end of the catch may move in a horizontal plane.With this, less parts are needed, and thus the locking mechanism may besimplified, without compromising a tight and safe locking of the two legmembers.

A perspective of an embodiment of the catch 34 is shown in FIG. 3 b. Thecatch has a cavity 40 formed therein. The sliding bar 33 of the secondleg member 41 is slidably received in the cavity 40 of the catch 34 (seeFIG. 3 a). The cavity 40 may be cylindrical in shape, although othershapes are possible. The catch has a stopping surface 47. The stoppingsurface may comprise the inner shell of the cavity 40. Preferably, thestopping surface includes the edge 45 of the cavity 40 with the outersurface 54 of the catch 34. At the bottom of the catch 34, a similaredge exists. Additionally, another cavity 49 may second U-shaped cavity49 is provided in the catch.

The operating of the locking mechanism 30 will be explained next. In alocked position, shown in FIGS. 4 a and 4 b, the transmission rod 31 isin an upward position, wherein hinge point 51 of the cam 36 is alsolifted upwards. The outer surfaces of the cam is designed in order toenable the catches 34,35 to rotate or tilt towards the centre of thehouse 32. When tilted, different parts of the stopping surface 47 of thecavity 40 of a catch 34,35 will engage the sliding bar 33. Morespecifically, at least the two edges 45 of the cavity 40 that willengage the sliding bar 33. Hereby, parts of the two edges 45 on bothsides of the cavity 40 will contact the sliding bar 33. The edges maypress into the sliding bar. The edges may also cut into the sliding bar33. This ensures that a high locking pressure is obtained, and preventsthe relative movement of the two leg members. The upper edge 45, and thelower edge engage with parts that are facing each other. Therefore,opposite perimeter parts of the second leg member 41, i.e. the slidingbar 33 are engaged. This imposes a moment on the sliding bar 33. As aresult the sliding bar 33 is pressed to both the house 32 and to thestopping surfaces 47. The sliding bar 33 is thus jammed by the catch 34and the house 32. Each contact point will yield static friction, whichprevents the sliding bar 33 from sliding in the house 32. It willtherefore be impossible for the sliding rod to move, and thus elongationof the leg is impossible.

It is noted that only a single catch 34 may be sufficient in order tofix the sliding bar 33. The additional catch 35 is positionedlongitudinally from the first catch. This additional catch, incombination with the first catch 34 ensures a tight fix. It can be seenin FIG. 2 that the catches 34,35 will tilt in different directions. Withthis, prevention of movement in both directions is ensured. Also, atight fix is assured.

The springs 38,39 that are provided next to the catches 34,35 alsoensure that the catches 34,35 are rotated or tilted towards the centreof the house 32. The springs 38,39 ensure that the catches 34,35 arepushed towards a locked position. The springs 38,39 also ensure amincreased engagement of the stopping surfaces 47 on the sliding bar 33.With this, a tight and safe fix of the sliding bar 33 in the lockingmechanism is achieved. In the embodiment shown, the springs arepositioned parallel to, and around the sliding bar 33 of the second legmember 20. This positioning is compact and convenient, and allows foreasy assembly of the supporting element. Other positions are possiblehowever. Other means of biasing the catch towards a locking position arepossible. For instance, a spring that is positioned near to thetransmission bar 31, and connected to botch catches 34,35, may be usedto pull the two catches 34,35 towards each other, thus biasing the twocatches towards a locking position.

Unlocking the locking mechanism 30 may be done as follows. By rotatingthe pushing block 50 around pivot point 48, the transmission bar 31 ismoved downwardly. The result will be that the hinge point 51 of the cam36 will also move down. The cam and house are arranged such that thisdownward movement will result in rotation of the cam 36 around rotationpoint 51. The cam 36 is arranged such that the combined movement resultsin simultaneously tilting the two catches from a locking position to anopen position. The movement of the cam 36 will lead to movement of theupper and lower surfaces of the cam 36, resulting in a tilting movementof both catches 34,35 towards an outside part of the house 32.Resultantly, the stopping surface of the cavity will then be positionedat a certain distance from the sliding bar 33, enabling movement of thesliding bar within the house 32. With this, the leg of the ladder may beextended or shortened in an axial direction.

It is noted that in a locked position of the locking mechanism, the cam36 may freely rotate around hinge point 51. It is possible that theouter surfaces of the cam are not in direct contact with the catches34,35. In that case, movement of the transmission bar 31 may benecessary to bring the outer surfaces of the cam into contact with thecatches, enabling movement of the catches towards an open position. Withthis, the locking mechanism may only be brought to an open position byactual movement of the transmission bar. This ensures that the userintends to open the locking mechanism, and prevents accidental openingof the locking mechanism.

In an unlocked position, a longitudinal axis of the cavity 40 extendsparallel to the sliding bar 33. This ensures that the area through whichthe sliding bar 33 may be slided is maximal, i.e. that there is amaximal aperture for the sliding bar 33. Accidental lock-ups may beprevented with this.

In an unlocked position, the spring 44 around the sliding bar 33 biasesthe extendible leg part 41 towards an extended position. Preferably, theforce of the spring is designed such that it balances the weighing forceof the object to be supported. This way, releasing the locking mechanism30 will only result in the extendable leg being extendable, withoutactually sliding within the house 32. Releasing the locking mechanismtherefore does not result in an active shortening of the extendible legdue to gravitational forces. When multiple legs are used, the force ofeach spring is chosen such that the combined forces of the springsbalance the weighing force of the object to be supported. The multiplesprings may each have a different spring force, dependent on the weightdistribution of the object to be supported. An object, such as a ladder,provided with a number of supporting elements according to thisembodiment, is relatively easy to position in any desired fashion. Theeffort needed to change the orientation of the object is relativelysmall, since the object is more or less self supported by the biasedsprings.

When the rotational force on the pushing block 50 is removed, theactions of the springs 38,39 near the catches 34,35, as well as theactions of the spring 43 near the transmission rod 31, will lead thetransmission rod to move upwards, thereby locking the locking mechanism30.

It is desired that an object having several extendable legs, such as aladder, may be operated by a central operating mechanism. FIG. 6 andFIG. 7 show an embodiment of an operating mechanism 60 suitable for thistask. The operating mechanism 60 comprises two turning rods 68,positioned at a distance from each other. The turning rods 68 may bepositioned mainly parallel in a flat surface, such as is shown in FIG.4. The turning rods 68 are connected by means of a connecting rod 64,65.The connecting rod 64,65 is connected to each turning rod 68 by means ofa bulge 66,67. At each outer end of the turning rods 68 pushing blocks62 are positioned. The pushing blocks are rigidly connected to theturning rods 68. At a lower surface of each pushing block 62,transmission bars 63 are provided. In the embodiment shown, thetransmission bars 63 engages the lower surface of the pushing block 62,and no fixed connection is present between the two. The transmissionbars 63 may be connected to a locking mechanism, as described earlier.At one end of one turning rod 68, a handle 61 is provided. The handlemay be used by someone for operating the locking mechanisms of severalextendable leg portions all at once. It is noted that the operatingmechanism shown in FIG. 6 may be used in combination with any supportingelement, regardless of the kind of locking mechanism used in thesupporting element.

By rotating the handle 61 in the direction of arrow A1, the turning rodis rotated. The rigid connection between the two turning rods, theconnection being formed by rigid connecting rod 64,65, will move also indirection of arrow A2. This results in a likewise rotation of the secondrod 68. Thus, both rods 68 will rotate over an equal angle. Also, allpushing blocks 62 will rotate equally, thereby pushing each transmissionbar 63 in a downward direction. As described before, the downwardmovement of the transmission bar 63 will enable a locking mechanism toget to an idle state. With this, an extendable leg may be positioned inany desired fashion.

It is pointed out that the extension of the leg is not coupled in anymanner to the transmission bar 63. As can be seen from FIG. 2, thetransmission bar 63 will only be used for locking and unlocking thelocking mechanism of an extendable leg. It is therefore noted that allleg members may be extended independently from each other. In otherwords, the length of each of the leg members may be chosen arbitrarily.The length of one leg does not form a restriction to the length ofanother leg. Thus, the user may adapt each of the extendible legs of anobject in any manner desirable. These degrees of freedom enable a userto position the object at a desired height (within the limitations ofthe extendible legs), and also to position the object at a certain anglewith respect to the base on which the object is standing. An additionaladvantage is that the locking mechanism of each extendible leg may beoperated with a central operating mechanism, enabling the user to easilyset up his object. The object may be a table, or a ladder, or any otherobject benefitting from the use of extendible legs, such as for instancea tripod.

The supporting element may be assembled in a relatively fast and easyway. Assembly will be discussed with reference to FIGS. 4 and 5. First,the second leg member 20 may be prepared. The sliding bar 33 may bepositioned in the house 32, by sliding a lower end of the sliding barthrough the top opening of the house 32. During this step, the twocatches 34,35 and the two springs 38,39 may be installed. When thesliding bar is in place, the spring 44 may be fitted on the sliding bar.Next, the lower part 41 of the second leg member 20 may be attached.Then, the transmission bar 31 may be installed in the housing, bysliding the bar 31 into the intended top opening of the house 32. Thespring 43 is also positioned. When the bar 32 and spring 43 are inplace, the cam 36 may be connected and attached to hinge point 51.Furthermore, the guiding block 46 may be installed. It will be obviousfor a person skilled in the art, that the positioning of the sliding bar33 and the transmission bar 31 may be done in a different order. Thecombination of the locking mechanism 30, the second leg member 20 andthe transmission bar 31 with guiding block 46 may be slid into thehollow first leg member 22. The hollow first leg member may be anextruded profile. The house 32 and other parts may be aligned in amethod known to a skilled person, and may then be attached to the secondleg member using fastening means, such as for instance rivets.

FIG. 8 a shows a further embodiment of a leg or supporting element 100having a locking element 101. A house 102 is mounted in a first legmember 103. A transmission element 104 is formed by a rod. It can beconnected to a central operating mechanism at a distance from thelocking mechanism. Due to the rod's stiffness a movement in theoperating mechanism can be transferred to the locking mechanism 101.Transmission element 104 can move axially in the leg 100 according toarrow 105. The movement can be guided by house 102 having a suitablebore receiving the transmission element 104.

A biasing element 109 provides a biasing force in the direction of arrow110 on the transmission element 104.

Transmission element 104 has a first pin 106. Further a hinge 107 isprovided connected to cam 108. Cam 108 rests on a house part 112.

From the position shown in FIG. 8 a, transmission element 104 can movein the direction of arrow 110 to the position shown in FIG. 8 b. FIG. 8a shows a locking position of the locking mechanism 101 and FIG. 8 bshows a unlocked position.

If the transmission element 104 is moved, cam 108 will rotate accordingto arrow 113 around hinge 107. A tip 114 of cam 108 engage catch 120.Simultaneously pin 106 will engage catch 121. Catches 120 and 121 canhave an embodiment similar to FIG. 3 b.

End parts 123,124 of the catches 120 and 121 are received in a cavity inhouse 102 and allow a tilting motion of the catches according to arrow125 and 126 respectively.

The catches 120, 121 have a cavity receiving a second leg member 130. Abiasing element 131, e.g. a spring, engages on the housing 102 and thesecond leg member 130 providing a biasing force towards extending theleg or support member 100 in the axial direction. Second leg member 130is received telescopically in the first leg member 103 and can slide inthe axial direction 105.

In the position according to FIG. 8 a, the cavities in the catches120,121 are tilted and a perimeter of the cavities will engage on theouter surface of the second leg member 130. If tilted sufficiently theengaging force will lock the second leg member in a locked position andthe leg or support element 100 will have a fixed length.

A further biasing element 140, again a spring in this embodiment,surrounds the second leg member 130 in this embodiment. Biasing element140 engages on both catches 120,121 and provides a force in the axialdirection, forcing the catches away from each other.

If moved to the unlocked position according to FIG. 8 b, the second legmember 130 can move freely with respect to the first leg member 103 orhouse 102 and the length of the leg 100 can be axially adapted. Thebiasing element 131 biases in the extended direction.

The biasing force in the extended direction can e.g. be similar to themass of the supporting element 100. In an embodiment the biasing forceis similar to the mass near an equilibrium position/length of the leg100. This will provide a ‘floating sensation’ if the apparatus to whichthe leg 100 is connected is positioned on a surface.

Second leg member 130 has a stop 133 that can engage on house 101limiting the length of axial extension.

From the unlocked position according to FIG. 8 b, the locking mechanismcan be brought to the locked position by axially moving the transmissionelement 104, allowing the catches to tilt according to arrows 125, 126,away from each other, biased by the biasing element 140.

As a result of unlocking, leg member 130 moved upwards by a distanceindicated by arrow 136. The part 135 of leg member 130, directlyconnected to the leg member, was guided in the frame of the first legmember 103 over the same distance 136 in a sliding arrangement.

By moving a distance 136 upwards, the biasing force from spring coil 131was overcome resulting in a work load W. This work could be provided bythe mass/weight of the ladder/table that the support 100 supports. Theweight of the ladder/table is now supported by the support 100 and inparticular the spring 131, resulting in a sort of floating sensation foran operator pushing against the first leg member 101.

In an embodiment a further pin can be positioned on the transmissionelement at the other side of catch 121.

In another embodiment a further biasing element can be positioned aroundtransmission element 104 between catches 120 and 121, biasing thecatches 120,121 in the tilted position according to FIG. 8 a.

Variations on the embodiments shown are imaginable, without divertingfrom the main notion of the invention. It will be clear that theinvention is described by using preferred embodiments. The invention isnot intended to be limited to these embodiments.

1-20. (canceled)
 21. Apparatus comprising a frame having at least threelegs for positioning the apparatus on a surface, wherein each of the atleast three legs are individually and selectively axially extendible foradjusting the length of each of the at least three legs, wherein the atleast three legs each comprise a transmission element and a lockingelement, the locking element having a locking position for locking theaxial extension of the leg, and having an open position for enablingaxial extension of the leg, wherein the at least three locking elementsare connected to a central operating mechanism via the transmissionelements, the central operating mechanism being arranged for activatingand deactivating the at least three locking elements simultaneously. 22.Apparatus according to claim 21, wherein at least two legs are hingeablyconnected with respect to each other and wherein the central operatingmechanism is arranged for activating and deactivating the lockingelements in the at least two legs hingeably connected with respect toeach other.
 23. Apparatus according to claim 21, wherein the operatingmechanism comprises a operating handle connected to a rod that isrotatably attached to the frame, the rod comprising at least two pushingblocks that are positioned at a distance from each other, wherein eachpushing block is arranged for engaging one of the transmission elements,wherein the operating mechanism is arranged such that rotation of therod by rotating the operating handle results in a translational movementof the transmission element by pushing of the pushing blocks, andwherein the transmission element is arranged such that a translationalmovement of the transmission element results in tilting movement of thecatch of the locking element.
 24. Apparatus according to claim 21,wherein the apparatus comprises a supporting platform, from which the atleast three legs extend downwardly.
 25. Apparatus according to claim 21,wherein the apparatus is a ladder.
 26. Apparatus according to claim 21,wherein the leg comprises a first leg member and a second leg member,wherein the first leg member is axially movable relative to the secondleg member for axially extending the leg, and wherein the first legmember comprises a house that is arranged for slidably receiving thesecond leg member (20), and wherein the locking element is received inthe house, the locking element comprising a catch that is tiltablymovable within the house for alternately acquiring the locking positionand the open position of the locking element, wherein the catchcomprises a cavity receiving the second leg member, wherein the catchcomprises a stopping surface surrounding the perimeter of the cavity,wherein the stopping surface is arranged for engaging at least twoopposed perimeter parts of the second leg member in a locking positionof the locking element,
 27. Apparatus according to claim 26, wherein alongitudinal axis of the cavity extends parallel to the second legmember in an open position.
 28. Apparatus according to claim 26, whereina further biasing element biases the catch towards the locking position.29. Apparatus according to claim 26, wherein the locking elementcomprises an additional catch that is tiltably movable within the housefor alternately acquiring the locking position and the open position ofthe locking element, wherein the additional catch comprises a cavityreceiving the second leg member, wherein the catch comprises a stoppingsurface surrounding a perimeter of the cavity, wherein the stoppingsurface is arranged for engaging at least two opposed perimeter parts ofthe second leg member in a locking position of the locking element,wherein the stopping surfaces of the catches surround differentlongitudinal parts of the second leg member.
 30. Apparatus according toclaim 29, wherein the catch and the additional catch are arranged fortilting in opposite directions towards a locking position.
 31. Apparatusaccording to claim 30, wherein a biasing element is positioned betweenthe catch and additional catch biasing the catches away from each other.32. Apparatus according to claim 31, wherein the biasing element ispositioned around the leg member.
 33. Apparatus according to claim 39,wherein the locking element comprises a cam that is provided in thehouse, wherein opposite sides of the cam engage the two catches, andwherein the cam is arranged for simultaneously tilting the two catchesfrom a locking position to an open position.
 34. Apparatus according toclaim 26, wherein the house further comprises a cam engaging the catchfor operating the catch from a locking position to an open position. 35.Apparatus according to claim 34, wherein the transmission element isconnected to the cam.
 36. Apparatus according to claim 21, wherein theleg comprises a first leg member and a telescopic second leg member. 37.Apparatus according to claim 21, wherein the leg further comprises abiasing element for biasing the leg towards an axially extendedposition.
 38. Apparatus according to claim 21, wherein a further biasingelement biases the locking element towards the locking position. 39.Apparatus comprising a frame having at least one hingeable leg forpositioning the apparatus on a surface, wherein the leg is individuallyand selectively axially extendible for adjusting the length of the leg,wherein the leg comprises a transmission element and a locking element,the locking element having a locking position for locking the axialextension of the leg, and having an open position for enabling axialextension of the leg, wherein the locking element is connected via thetransmission element to a central operating mechanism fixed to theframe, the central operating mechanism being arranged for activating anddeactivating the locking element.